[Bug tree-optimization/100366] spurious warning - std::vector::clear followed by std::vector::insert(vec.end(), ...) with -O2

[mrsam--- via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100366

--- Comment #8 from Sam Varshavchik <mr...@courier-mta.com> ---
If the warning is spurious, then changing vector.tcc won't, of course, keep it
from popping up elsewhere when the same sequence of events get triggered.

Here, it drew my attention to the missed micro-optimization of using reserve(),
which had the benefit of avoiding the warning and allowing me to keep the
-Werror option.